A frequent way today to restore a damaged limb, such as lost tooth, is to install a fixture in the adjacent bone tissue and replace the damaged parts. In this respect, for a successful result, the fixture should become fully stable and correctly joined to the bone. The term osseointegration is used for this joining effect, the basic meaning of this term being the bone tissue growth into the fixture surface. The two major contributors to this joint are a mechanical joint and an organic joint. The former being generally influenced by the macro geometry of the bore into which the fixture is installed, and by the macro geometry of the fixture, and is a direct effect of how well these two work together. The latter one being a continuously evolving and developing effect, particularly the time immediately after installation, and being generally influenced by how well the micro surface structure of the fixture interacts with the bone tissue.
Due to ingrowth there will be an interlocking effect between the bone and the fixture. Also, the mechanical joint is developed over time since the bone tissue, under ideal conditions, may grow into surface cavities of the fixture, and grow into voids left between the fixture and the bore after installation.
During installation of a fixture into the bone tissue, the bone is subjected to both stress and strain. The relationship between stress and strain is substantially linear up to a yield point (yield strain). Up to the yield point the bone is deformed elastically. However, beyond the yield point the bone will deform plastically. In order to provide for good healing conditions and stability of the fixture in the bone, care is taken to maintain the elasticity of the bone tissue and to avoid exceeding the yield point.
There is a continuous endeavour in the industry to further increase the stability of fixtures implanted in bone tissue and to improve the basic conditions during the healing phase after fixture installation. One example is the provision of the fixture surface with different types of structures, such as micro-roughened or blasted structures for increasing the contact surface between the fixture and the bone.
Nevertheless, there is till room for further development of fixtures as regards their stability in bone tissue.